EP3464433A1

EP3464433A1 - Process for producing expandable polylactic acid-containing pellets

Info

Publication number: EP3464433A1
Application number: EP17728499.9A
Authority: EP
Inventors: Bangaru Dharmapuri Sriramulu Sampath; Jerome LOHMANN; Peter Gutmann
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2016-06-07
Filing date: 2017-06-01
Publication date: 2019-04-10
Anticipated expiration: 2037-06-01
Also published as: CN109312093B; WO2017211660A1; CA3026811A1; CN109312093A; US20190127545A1; CA3026811C; EP3464433B1; AU2017276585A1; US10787554B2; JP6918025B2; JP2019523799A; BR112018074284B1; ES2854976T3; KR20190015758A; AU2017276585B2; BR112018074284A2; KR102326407B1

Abstract

The invention relates to a process for producing expandable polylactic acid-containing pellets, comprising the steps of: a) melting and mixing in the following components: i) 65% to 95% by weight, based on the total weight of components i to iii, of polylactic acid, where the polylactic acid is composed of proportions of: ia) 65% to 95% by weight of polylactic acid having a D-lactic acid content of 0.3% to 5% by weight and ib) 5% to 3% by weight of polylactic acid having a D-lactic acid content of 10% to 18% by weight; ii) 15% to 35% by weight, based on the total weight of components i to iii, of an aliphatic polyester selected from the group consisting of polybutylene succinate, polybutylene succinate-co-adipate and polybutylene succinate-co-sebacate; iii) 0% to 2% by weight, based on the total weight of components i to iii, of a compatibilizer; iv) 0.1% to 5% by weight, based on the total weight of components i to iii, of an additive, b) mixing v) 1% to 7% by weight, based on the total weight of components i to iv, of an organic blowing agent and vi) 0.01% to 5% by weight of a co-blowing agent – selected from the group of nitrogen, carbon dioxide, argon, helium and mixtures thereof – into the polymer melt by means of a static or dynamic mixer at a temperature of at least 140°C, c) discharging through a die plate having bores having a diameter at the die exit of not more than 1.5 mm and d) pelletizing the blowing agent-containing melt directly beyond the die plate underwater at a pressure in the range from 1 to 21 bar.

Description

Process for the preparation of expandable polylactic acid containing granules

The invention relates to a process for the preparation of expandable polylactic acid-containing granules, comprising the steps:

Melting and mixing of the components:

i) from 65 to 95% by weight, based on the total weight of components i to iii, of polylactic acid, where the polylactic acid comprises in part: ia) from 65 to 95% by weight of polylactic acid with a D-lactic acid content of 0.3 to 5% and ib) 5 to 35% by weight of polylactic acid having a D-lactic acid content of 10 to 18%; ii) from 15 to 35% by weight, based on the total weight of components i to iii, of an aliphatic polyester selected from the group consisting of polybutylene succinate, polybutylene succinate-coadipate and polybutylene succinate cosebacate;

iii) 0 to 2% by weight, based on the total weight of components i to iii, of a compatibilizer;

iv) from 0.1 to 5% by weight, based on the total weight of components i to iii, of an additive,

Interfere

v) 1 to 7 wt .-% based on the total weight of components i to iv, an organic blowing agent and

vi) from 0.01 to 5% by weight of a co-propellant - selected from the group of nitrogen, carbon dioxide, argon, helium or mixtures thereof - in the polymer melt by means of a static or dynamic mixer at a temperature of at least 140 ° C,

Discharge through a nozzle plate with holes whose diameter at the nozzle outlet is at most 1, 5 mm and

Granulating the blowing agent-containing melt directly behind the nozzle plate under water at a pressure in the range of 1 to 21 bar.

Process for the preparation of expandable polylactic acid-containing granules (polylactic acid-containing particle foams) are described in WO 2001/012706 and in particular WO 201 1/086030. The expandable, propellant-containing, polylactic acid-containing granules described therein, however, can not fully convince in terms of their storage stability.

WO 2008/130226 and JP2007 169394 describe expanded or expandable particle foams having densities of 10 to 100 g / l, which are already prefoamed and can be re-impregnated with blowing agent. In such particle foams, the storage stability does not play such a major role, since they are at the time of Transports to the end user (storage period) contain no or almost no propellant.

The object of the present invention was to provide a simple, process-capable process for the production of expandable, propellant-containing polylactic acid-containing granules with improved storage stability.

Accordingly, the method described above was found. The process according to the invention is described in more detail below.

The polylactic acid-containing polymer prepared in step a) is usually a mixture of: i) 65 to 95% by weight, preferably 70 to 79.9% by weight, based on the total weight of components i to iii, polylactic acid, wherein the polylactic acid proportionally from ia) 65 to 95 wt .-%, preferably 80 to 95 wt .-%, polylactic acid having a D-lactic acid content of 0.3 to 5% and ib) 5 to 35 Wt .-%, preferably 5 to 20 wt .-%, polylactic acid having a D-lactic acid content of 10 to 18%; ii) from 15 to 35% by weight, preferably from 20 to 29.9% by weight, based on the total weight of components i to iii, of at least one polyester selected from the group consisting of polybutylene succinate, polybutylene succinate-coadipate and polybutylene succinate cosebacate; iii) 0 to 2% by weight, preferably 0.1 to 1% by weight, based on the total weight of components i to iii, of a compatibilizer, preferably a peroxide or an epoxide group-containing copolymer based on styrene, acrylic ester and / or or methacrylic acid ester, and iv) 0 to 5 wt .-%, preferably 0.1 to 1 wt .-%, based on the total weight of components i to iii, of one or more nucleating agent, preferably talc.

As component i) is polylactic acid as a mixture of ia) 65 to 95 wt .-% of a semicrystalline polylactic acid having a D-lactic acid content of 0.3 to 5% and ib) 5 to 35 wt .-% of an amorphous polylactic acid with used a D-lactic acid content of 10 to 18%.

Preferably, a semicrystalline polylactic acid having the following property profile is used: A melt volume rate (MVR at 190 ° C. and 2.16 kg according to ISO 1 133) of 0.5 to 15, preferably 1 to 9, particularly preferably 2 to 8 ml / 10 minutes

• a melting point below 180 ° C;

· A glass point (Tg) greater than 40 ° C

• a water content of less than 1000 ppm

• a residual monomer content (lactide) of less than 0.3%.

• a molecular weight greater than 50,000 daltons. Preferred polylactic acids are, for example, from NatureWorks the Ingeo® 2003 D, 4032 D, 4042 D and 4043 D, 3251 D, 3052 D and in particular 8051 D and 8052 D. Ingeo® 8051 D and 8052 D are polylactic acids from NatureWorks, with the following product properties: Tg: 65.3 ° C, Tm: 153.9 ° C, MVR: 6.9 [ml / 10 minutes], M _w : 186000, Mn: 107000 and a D-Michsäureanteil of less than 5%. Furthermore, these products have a slightly higher acid number.

Amorphous polylactic acid has a proportion of D-lactic acid greater than 10, but usually not higher than 18%. A particularly suitable amorphous polylactic acid is available from NatureWorks under the trade name Ingeo® 4060 D with a D-lactic acid content of 1 1 to 13%. Other polylactic acid examples of NatureWorks are the Ingeo 6302D, 6362D and 10361D.

Component ii is to be understood as meaning aliphatic polyesters selected from the group consisting of polybutylene succinate, polybutylene succinate-coadipate and polybutylene succinate cosebacate.

The aliphatic polyesters are marketed by Showa Highpolymers under the name Bionolle and by Mitsubishi under the name GSPIa or BioPBS. More recent developments are described in WO 2010/03471 1.

The aliphatic polyesters generally have viscosity numbers according to DIN 53728 of 150 to 320 cm ³ / g and preferably 150 to 250 cm ³ / g.

MVR (melt volume rate) according to EN ISO 1133 (190 ° C, 2.16 kg weight) is generally 0.1 to 70, preferably from 0.8 to 70 and in particular from 1 to 60 cm ^3/10 min.

The acid numbers according to DIN EN 12634 are generally from 0.01 to 3 mg KOH / g, preferably from 0.01 to 2.5 mg KOH / g.

Preferably used polyesters ii contain: a) 80 to 100 mol%, preferably 90 to 99.5 mol%, based on the components a to b, succinic acid; 0 to 20 mol%, preferably 0.5 to 10 mol%, based on the components a to b, adipic acid or sebacic acid;

85 to 100 mol%, preferably 98 to 100 mol%, based on the components a to b, 1, 3 propanediol or 1, 4-butanediol.

0 to 15 wt .-%, preferably 0.1 to 2 wt .-%, based on the total weight of components a to c, of a chain extender and / or crosslinker selected from the group consisting of: a polyfunctional isocyanate, such as preferably hexamethylene diisocyanate; isocyanurate; oxazoline; Epoxide and / or an at least trifunctional alcohol such as preferably glycerol.

The compatibilizer iii) is described in more detail below.

Peroxides are understood as meaning, for example, the products marketed by Akzo under the brand name Trigonox, for example Trigonox 301.

Epoxides are understood as meaning, in particular, epoxide-group-containing copolymer based on styrene, acrylic acid ester and / or methacrylic acid ester. The epoxy groups bearing units are preferably glycidyl (meth) acrylates. Copolymers having a glycidyl methacrylate content of greater than 20, particularly preferably greater than 30 and especially preferably greater than 50% by weight, of the copolymer have proved to be advantageous. The epoxy equivalent weight (EEW) in these polymers is preferably 150 to 3000, and more preferably 200 to 500 g / equivalent. The weight average molecular weight Mw of the polymers is preferably from 2,000 to 25,000, in particular from 3,000 to 8,000. The average molecular weight (number average) M _{n of} the polymers is preferably from 400 to 6,000, in particular from 1,000 to 4,000. The polydispersity (Q) is generally between 1.5 and 5. pen epoxide group-containing copolymers of the above type are sold for example by BASF Resins BV under the trademark Joncryl ^® ADR. Particularly suitable as compatibility agent is Joncryl ^® ADR 4368 or Joncryl ADR 4468C or Joncryl ADR 4468HP.

The compatibilizer is added in 0 to 2 wt .-%, preferably 0.1 to 1 wt .-%, based on the total weight of components i to iii). Component iv is understood as meaning 0.01 to 5% by weight of one or more of the following additives: stabilizer, nucleating agent, lubricant and release agent, surfactant, wax, antistatic agent, antifogging agent, dye, pigment, UV absorber, UV stabilizer. Stabilizer or other plastic additive. As already mentioned, the use of from 0.2 to 1% by weight, based on the components i and ii of a nucleating agent, is particularly preferred. Nucleating agent is to be understood in particular as meaning talc, chalk, carbon black, graphite, calcium or zinc stearate, poly-D-lactic acid, N, N'-ethylene-bis-12-hydroxystearamide or polyglycolic acid. Talcum is particularly preferred as nucleating agent.

Carbon black, chalk and graphite can also be considered as pigments; they may be added to the particle foam, such as iron oxide and other color pigments, to adjust a desired color. A paper-like appearance can be achieved advantageously by adding Sicoversal®, a color batch from BASF Color Solutions comprising carbon black, iron oxide and a yellow pigment. In general, the pigments iv-2 in a concentration of 0.1 to 1 wt, based on the

Reaction mixture used.

Component iv may contain further ingredients known to the person skilled in the art but not essential to the invention. For example, the usual additives in plastics technology such as stabilizers; Lubricants and release agents such as stearates (especially calcium stearate); Plasticizers such as citric acid esters (especially acetyl tributyl citrate), glyceric acid esters such as triacetylglycerol or ethylene glycol derivatives, surfactants such as polysorbates, palmitates or laurates; Waxes such as beeswax or beeswax esters; Antistatic, UV absorber; UV stabilizer; Antifog agent or dyes.

The propellant can be considered as a further component v.

The propellant-containing polymer melt generally contains one or more propellants in a homogeneous distribution in a proportion of 2 to 10 wt .-%, preferably 3 to 7 wt .-%, based on the propellant-containing polymer melt. Suitable blowing agents are the physical blowing agents commonly used in EPS, such as aliphatic hydrocarbons having 2 to 7 carbon atoms, alcohols, ketones, ethers, amides or halogenated hydrocarbons. Preference is given to using isobutane, n-butane, n-pentane and, in particular, isopentane. Further preferred are mixtures of n-pentane and iso-pentane.

The amount of blowing agent added is chosen such that the expandable granules have an expansion capacity a, defined as bulk density before prefoaming of 500 to 800 and preferably 580 to 750 kg / m ³ and a bulk density after pre-foaming of at most 125, preferably 8 to 100 kg / m ³ have. When using fillers, depending on the type and amount of the filler, bulk densities in the range of 590 to 1200 kg / m ³ may occur.

To prepare the expandable granules according to the invention, the blowing agent is mixed into the polymer melt. The process comprises stages A) melt production, B) mixing C) conveying and D) granulating. Each of these stages can be carried out by the apparatuses or apparatus combinations known in plastics processing. For mixing, static or dynamic mixers are suitable, for example extruders. The polymer melt can be produced directly by melting polymer granules. If necessary, the melt temperature can be lowered via a cooler. For example, pressurized underwater granulation, granulation with rotating knives and cooling by spray misting of tempering liquids come into consideration for the granulation. Apparatus arrangements suitable for carrying out the method are, for example:

Extruder - static mixer - cooler - granulator

Extruder - Granulator

Furthermore, the arrangement may include a side extruder for introducing additives, e.g. of solids or thermally sensitive additives.

The propellant-containing polymer melt is usually conveyed through the nozzle plate at a temperature in the range from 140 to 300.degree. C., preferably in the range from 160 to 270.degree.

In order to obtain marketable granule sizes, the diameter (D) of the nozzle bores at the nozzle exit should be in the range from 0.1 to 2 mm, preferably in the range from 0.1 to 1.2 mm, particularly preferably in the range from 0.1 to 0.8 mm lie. This granulate sizes below 2 mm, especially in the range 0.2 to 1, 4 mm can be adjusted specifically after strand expansion.

The strand expansion can be influenced by the geometry of the die, apart from the molecular weight distribution. The nozzle plate preferably has bores with a ratio L / D of at least 2, the length (L) designating the nozzle region whose diameter corresponds at most to the diameter (D) at the nozzle exit. Preferably, the ratio L / D is in the range of 3 to 20.

In general, the diameter (E) of the holes at the nozzle inlet of the nozzle plate should be at least twice as large as the diameter (D) at the nozzle outlet. An embodiment of the nozzle plate has bores with conical inlet and an inlet angle α less than 180 °, preferably in the range of 30 to 120 °. In a further embodiment, the nozzle plate has bores with conical outlet and an outlet angle ß smaller than 90 °, preferably in the range of 15 to 45 °. In order to produce specific granule size distributions of the polymers, the nozzle plate can be equipped with bores of different exit diameters (D). The various embodiments of the nozzle geometry can also be combined. In general, the granules have an average diameter in the range of 0.1 to 2 mm and 50 to 300 cavities / mm ² cross-sectional area. By lowering the temperature in the underwater granulation, the bulk density can the be reduced to the range of 580 to 750 kg / m ^3, preferably 580 to 720kg / m ^3. Furthermore, the expandable polylactic acid-containing granules thus produced have an increased storage stability. The increased storage stabilities of the granules produced according to the invention are in particular a) the method of pre-nucleation by the use of a combination of organic blowing agent v and co-blowing agent vi and b) on the use of a mixture of semicrystalline and amorphous component i in the indicated attributable to narrow mixing ratios. They can be foamed easily after weeks.

By the use of volatile, liquid / gaseous cavities forming co-blowing agent vi) a cellular structure can be adjusted in the expandable granules, with the aid of which the subsequent foaming process can be improved and the cell size can be controlled.

The method for adjusting this cavity morphology can also be referred to as a pre-nucleation, wherein the cavities are essentially formed by the co-propellant vi).

The co-propellant vi) forming the cavities differs from the actual propellant v in its solubility in the polymer. In the preparation of the first propellant v) and co-propellant vi) are completely dissolved in the polymer at sufficiently high pressure. Subsequently, the pressure is reduced, preferably within a short time, and thus the solubility of the co-propellant vi) is reduced. This results in a phase separation in the polymeric matrix and a vorukleierte structure arises. The actual propellant v) remains largely dissolved in the polymer due to its higher solubility and / or its low diffusion rate. Simultaneously to reduce the pressure, a temperature reduction is preferably carried out in order to prevent excessive nucleation of the system and to reduce outflow of the actual propellant v). This is achieved by co-propellant vi) in conjunction with optimum granulation conditions. Preferably, the co-propellant vi) escapes to at least 80 wt .-% within 24 h of the expandable thermoplastic particles when stored at 25 ° C, atmospheric pressure and 50% relative humidity. The solubility of the co-propellant vi) in the expandable thermoplastic particles is preferably below 0.1% by weight. In all cases, the added amount of the co-propellant vi) used in the pre-nucleation should exceed the maximum solubility under the present process conditions. Therefore, co-blowing agents vi) are preferably used, which have a low but sufficient solubility in the polymer. These include in particular gases such as nitrogen, carbon dioxide, air or noble gases, more preferably nitrogen, whose solubility in many polymers is reduced at low temperatures and pressures. But there are also other liquid additives conceivable.

Particular preference is given to using inert gases such as nitrogen and carbon dioxide. In addition to their suitable physical properties, both gases are distinguished by low costs, good availability, easy handling and inert or inert behavior. For example, in the presence of the two gases, in almost all cases, no degradation of the polymer takes place. Since the gases themselves are extracted from the atmosphere, they also have an environmentally neutral behavior. The amount of co-propellant (vi) used should be: (a) sufficiently small to dissolve at the given melt temperatures and pressures during melt impregnation until granulation; (b) be sufficiently high to segregate and nucleate at the granulation water pressure and granulation temperature from the polymer. In a preferred embodiment, at least one of the blowing agents used is gaseous at room temperature and under atmospheric pressure.

Particular preference is given to using talc as nucleating agent iv) in combination with nitrogen as co-blowing agent vi). Metallic barrels and octabins are used, among other things, for the transport and storage of the expandable granules. When using barrels, it must be taken into account that the release of the co-propellants vi) can possibly build up pressure in the drum. As packaging, therefore, preferably open containers such as octabins or barrels are to be used, which allow a pressure reduction by permeation of the gas from the barrel. Drums which allow the co-propellant (vi) to diffuse out and minimize or prevent out-diffusion of the actual propellant (v) are particularly preferred. This can for example be made possible by the vote of the sealing material on the blowing agent or co-blowing agent vi). Preferably, the permeability of the sealing material for the co-propellant vi) is at least a factor of 20 higher than the permeability of the sealing material for the propellant v) By Vornukleierung, for example by adding small amounts of nitrogen and / or carbon dioxide, a cellular morphology can be adjusted in the expandable, propellant-containing granules. The average cell size in the center of the particles may be larger than in the peripheral areas, the density in the peripheral areas of the particles may be higher. As a result, blowing agent losses are minimized as much as possible.

By Vornukleierung a significantly better cell size distribution and a reduction of the cell size after pre-foaming can be achieved. In addition, the required amount of blowing agent to achieve a minimum bulk density is lower and the storage stability of the material is improved. Small amounts of nitrogen or carbon dioxide when added to the melt can lead to a significant shortening of the prefoaming times at a constant blowing agent content or to a significant reduction in blowing agent quantities with constant foaming times and minimal foam densities. In addition, pre-nucleation improves product homogeneity and process stability.

Further impregnation of the polymer granules according to the invention with blowing agents is furthermore possible much faster than with granules of identical composition and more compact, ie. H. noncellular structure. On the one hand, the diffusion times are lower, on the other hand, similar to directly impregnated systems, lower blowing agent amounts are required for foaming.

Finally, by Vornukleierung the blowing agent content, which is required to achieve a certain density is reduced, and thus the demolding times in the molding or block production can be reduced. Thus, the processing costs can be reduced and the product quality can be improved.

The principle of pre-nucleation can be used both for suspension technology and for melt impregnation technology for the production of expandable particles. Preference is given to the use in the melt extrusion process, in which the addition of the co-blowing agent vi) is granulated by the pressure-assisted underwater granulation after the exit of the blowing agent-laden melt. By selecting the granulation parameters and co-propellant vi), the microstructure of the granules can be controlled as described above.

For higher amounts of co-propellant vi), for example in the range of 1 to 5% by weight based on the propellant-containing polymer melt, a lowering of the melt temperature or the melt viscosity and thus a significant increase in throughput is possible. Thus, a gentle incorporation of thermolabile additives, for example flame retardants, to the polymer melt is also possible. The composition of the expandable thermoplastic particles is not altered by this, since the co-blowing agent in the melt extrusion essentially differs. To utilize this effect, CO2 is preferably used. At N2 the effects on the viscosity are lower. Nitrogen is therefore used predominantly to set the desired cell structure.

The liquid-filled chamber for granulating the expandable thermoplastic polymer particles is preferably operated at a temperature in the range of 20 to 80 ° C, more preferably in the range of 30 to 60 ° C.

In order to keep the thermal degradation of the polylactic acid as low as possible, it is also expedient to keep the mechanical and thermal energy input as low as possible in all process stages. The mean shear rates in the screw channel should be low, shear rates below 250 / sec, preferably below 100 / sec, and temperatures below 270 ° C. and short residence times in the range from 2 to 10 minutes in stages c) and d) are preferably maintained. The residence times are without cooling step usually at 1, 5 to 4 minutes and when a cooling step is provided usually at 5 to 10 minutes. The polymer melt can by pressure pumps, z. B. gear pumps funded and discharged.

To improve processability, the finished expandable granules may be coated by glycerol esters, antistatic agents or anticaking agents.

The expandable granules according to the invention have a lower bond to granules containing low molecular weight plasticizers, and are characterized by a low pentane loss during storage.

The expandable granules according to the invention can be prefoamed in a first step by means of hot air or water vapor into foam particles having a density in the range from 8 to 100 kg / m ³ and welded in a second step in a closed mold to particle moldings.

The granules produced by the process of the invention have a high biodegradability with good properties during foaming. For the purposes of the present invention, the feature "biodegradable" for a substance or a substance mixture is fulfilled if this substance or the substance mixture according to DIN EN 13432 has a percentage degree of biodegradation of at least 90%.

In general, biodegradability causes the granules or foams made therefrom to decay within a reasonable and detectable period of time. Degradation can be effected enzymatically, hydrolytically, oxidatively and / or by the action of electromagnetic radiation, for example UV radiation, and is usually effected for the most part by the action of microorganisms such as bacteria, yeasts, fungi and algae. The biodegradability can be quantified, for example, by mixing the polyester with compost and using it for a specific be stored te time. For example, according to DIN EN 13432, C02-free air is allowed to flow through ripened compost during composting. The compost is subjected to a defined temperature program. Here, the biodegradability is determined by the ratio of the net CC release of the sample (after deduction of C02 release by the compost without sample) to the maximum CC release of the sample (calculated from the carbon content of the sample) as a percentage of biodegradation Are defined. Biodegradable granules usually show after a few days of composting significant degradation phenomena such as fungal growth, crack and hole formation.

Other methods of determining biodegradability are described, for example, in ASTM D 5338 and ASTM D 6400-4.

Examples

Materials used: Component i:

i-1 a: aliphatic polyester, polylactide Natureworks® 8052 D from NatureWorks with a D lactic acid content of 4.5%

i-1 b: aliphatic polyester, polylactide Natureworks® 4060 D from NatureWorks with a D lactic acid content of 12%

Component ii:

ii-1: aliphatic polyester, polybutylene succinate GSPIa FZ91 PD from MCC component iii:

iii- 1: Joncryl® ADR 44688 C from BASF SE component iv:

iv-1: HP 325 Chinatalk Luzenac iv-2: color masterbatch (25% with carbon black, iron oxide and monoazo yellow pigment as additive and aliphatic polyester ii-1 as carrier) Sicoversal® from BASF Color Solutions

Component v:

v-1: Propellant: iso-pentane

Composed vi:

vi-1: co-propellant: nitrogen (N ₂ ) Comparative Example 1 (without component i-1 b)

6.7 parts of isopentane (component v-1) and 0.12 part of nitrogen (vi-1) were melted into 75 parts of component i-1 a, 25 parts of component ii-1, 0.2 part of component iii -1 and 0.3 parts of component iv-1 mixed at a melting temperature of 200-240 ° C.

The melt was conveyed at a rate of 70 kg / h through a die plate with 50 holes (diameter 0.65 mm) and a temperature of 260 ° C. With the help of a pressurized and tempered underwater pelletizer (20 bar - 40 ° C), pre-granulated granules with a narrow granule size distribution were produced.

The granules were stored for a certain time at room temperature or at 37 ° C and then by the action of flowing water vapor, the granules were prefoamed and welded in a second step in a closed mold to particle moldings.

The flexural strength and the bending work according to DIN-EN 12089 were determined on the molded parts

Example 2: (with 10% component i-1 b)

6.7 parts of isopentane (component v-1) and 0.12 part of nitrogen (vi-1) were dissolved in a melt of 65 parts of component i-1 a, 10 parts of component i-1 b, 25 parts of component ii. 1, 0.2 parts of component iii-1 and 0.3 parts of component iv-1 mixed at a melting temperature of 200-240 ° C.

The melt was conveyed at a rate of 70 kg / h through one with 50 bores (diameter 0.65 mm) and a temperature of 260 ° C. With the help of a pressurized and tempered underwater pelletizer (20 bar - 40 ° C), pre-granulated granules with a narrow granule size distribution were produced.

The flexural strength and the bending work according to DIN-EN 12089 were determined on the molded parts Comparative Example 3: (without component i-1 b, without component ii-1)

6.7 parts of iso-pentane (component v-1) and 0.12 part of nitrogen (vi-1) were added to a melt of 100 parts component i-1 a, 0.2 parts component iii-1 and 0.3 parts Component iv-1 mixed at a melting temperature of 200-240 ° C. The melt was conveyed at a rate of 70 kg / h through one with 50 bores (diameter 0.65 mm) and a temperature of 260 ° C. With the help of a pressurized and tempered underwater pelletizer (20 bar - 40 ° C), pre-granulated granules with a narrow granule size distribution were produced. The granules were stored for a certain time at room temperature or at 37 ° C and then by the action of flowing steam, the granules were prefoamed. Comparative Example 4 (without component ii-1)

6.7 parts of iso-pentane (component v-1) and 0.12 part of nitrogen (vi-1) were melted into 90 parts of component i-1 a, 10 parts of i-1 b, 0.2 part of component iii -1 and 0.3 parts of component iv-1 mixed at a melting temperature of 200-240 ° C.

The melt was conveyed at a rate of 70 kg / h through one with 50 bores (diameter 0.65 mm) and a temperature of 260 ° C. With the help of a pressurized and tempered underwater pelletizer (20 bar - 40 ° C), pre-granulated granules with a narrow granule size distribution were produced. The granules were stored for a certain time at room temperature or at 37 ° C and then by the action of flowing steam, the granules were prefoamed.

Comparative Example 5 (without component i-1 b and component vi-1)

6.7 parts of isopentane (component v-1) were melted into 90 parts of component i-1 a, 10 part i-1 b, 0.2 part of component iii-1 and 0.3 part of component iv-1 mixed at a melting temperature of 200-240 ° C.

Example 6: (with color masterbatch)

6.2 parts of iso-pentane (component v-1) and 0.12 part of nitrogen (vi-1) were dissolved in a melt of 69.4 parts of component i-1 a, 5 parts of component i-1 b, 24.9 Parts Component ii-1, 0.2 parts Component iii-1, 0.4 parts Component iv-1 and 0.3 parts Component iv-2 mixed at a melt temperature of 200-240 ° C.

The granules were stored for a certain time at room temperature or at 37 ° C. and then the granules were prefoamed by the action of flowing steam. Example 7: (with color masterbatch)

6.2 parts of iso-pentane (component v-1) and 0.12 part of nitrogen (vi-1) were dissolved in a melt of 69.4 parts of component i-1 a, 5 parts of component i-1 b, 24.1 Parts Component ii-1, 0.2 parts Component iii-1, 1, 2 parts Component iv-1 and 0.3 parts Component iv-2 mixed at a melt temperature of 200-240 ° C.

The melt was conveyed at a rate of 70 kg / h through one with 50 bores (diameter 0.65 mm) and a temperature of 260 ° C. With the help of a pressurized and tempered underwater granulation (20 bar - 40 ° C) pre-granulated granules with a narrow granule size distribution were produced.

The granules were stored for a certain time at room temperature or at 37 ° C and then by the action of flowing steam, the granules were prefoamed.

Example 8: (with color masterbatch)

6.2 parts of iso-pentane (component v-1) and 0.12 part of nitrogen (vi-1) were dissolved in a melt of 69.4 parts of component i-1 a, 5 parts of component i-1 b, 23.3 Parts Component ii-1, 0.2 parts Component iii-1, 2 parts Component iv-1 and 0.3 parts Component iv-2 mixed at a melt temperature of 200-240 ° C. The melt was conveyed at a rate of 70 kg / h through one with 50 bores (diameter 0.65 mm) and a temperature of 260 ° C. With the help of a pressurized and tempered underwater granulation (20 bar - 40 ° C) pre-granulated granules with a narrow granule size distribution were produced.

Example 9: (with color masterbatch)

6.2 parts of iso-pentane (component v-1) and 0.12 part of nitrogen (vi-1) were melted into 69.4 parts of component i-1 a, 5 parts of component i-1 b, 21, 3 Parts Component ii-1, 0.2 parts Component iii-1, 4 parts Component iv-1 and 0.3 parts Component iv-2 at a melt temperature of 200-240 ° C mixed. The melt was conveyed at a rate of 70 kg / h through one with 50 bores (diameter 0.65 mm) and a temperature of 260 ° C. With the help of a pressurized and tempered underwater pelletizer (20 bar - 40 ° C), pre-granulated granules with a narrow granule size distribution were produced. The granules were stored for a certain time at room temperature or at 37 ° C and then by the action of flowing steam, the granules were prefoamed.

V-Bsp-1 Bsp-2 V-Bsp-3 V-Bsp-4 V-Bsp-5

Min. Bulk density foam

26.4 24.1 21, 4 NA after production (kg / m ³ ) 22.0

Min. Bulk density foam

after 7 days storage at 26.2 24.4 21, 9 22.4 NA room temperature (kg / m ³ )

Min. Bulk density foam

after 14 days storage at 26.6 24.1 21, 8 22.3 NA room temperature (kg / m ³ )

Min. Bulk density foam

after 7 days storage at 51, 5 27.7 410 87 NA 37 ° C (kg / m ³ )

Min. Bulk density foam

after 14 days storage at 1 1 1, 0 60.0 560 302 NA 37 ° C (kg / m ⁵ ) Bending work according to DIN

EN 12089 (J / (kg / m ³ ))

0.06 0.14

14 days storage at

room temperature

NA: does not foam

With the process described in WO 08/130226 (see V-Bsp-5 without Vornukleie- tion and without the inventive component ii) is not reached to propellant-containing, expandable granules. The significantly improved process according to WO 11/086030 (see V-Bsp-1) provides propellant-containing, expandable granules which are stable in storage at room temperature for 2 weeks, but at higher temperatures, as they may happen during transport quite short term, are the Results less satisfactory. As shown in Example 2, the process according to the invention provides propellant-containing, expandable granules which are storage-stable even at relatively high temperatures.

In addition, the product of Example 2 shows better mechanical properties compared to Example 1.

Claims

claims:

Process for the preparation of expandable polylactic acid-containing granules, comprising the steps:

Melting and mixing of the components:

i) from 65 to 95% by weight, based on the total weight of components i to iii, of polylactic acid, wherein the polylactic acid comprises in part: ia) from 65 to 95% by weight of polylactic acid having a D-lactic acid content of from 0.3 to 5 % and ib) is 5 to 35% by weight of polylactic acid having a D-lactic acid content of 10 to 18%;

ii) from 5 to 35% by weight, based on the total weight of components i to iii, of an aliphatic polyester selected from the group consisting of polybutylene succinate, polybutylene succinate-coadipate and polybutylene succinate cosebacate;

ii) 0 to 2% by weight, based on the total weight of components i to ii, of a compatibilizer; and

v) 0.1 to 5% by weight, based on the total weight of components i to iii, of an additive,

Interfere

v) 1 to 7 wt .-%, based on the total weight of components i to iv, of an organic blowing agent and

vi) 0.01 to 5 wt .-% of a co-propellant - selected from the group consisting of nitrogen, carbon dioxide, argon, helium or mixtures thereof - in the polymer melt by means of a static or dynamic mixer at a temperature of at least 140 ° C,

A method according to claim 1, characterized in that the underwater graining is carried out at 20 to 80 ° C.

Process according to claims 1 or 2, characterized in that iso-pentane is used as the organic blowing agent in step b).

Process according to claims 1 to 3, characterized in that the melt in step a) is a color masterbatch containing iron oxide, carbon black and an organic yellow pigment is added.